Severe Weather Alert

Mayfly mayhem causing problems along riverways

PIERCE COUNTY, Wis. (WEAU) – It’s mayfly mayhem in parts of western Wisconsin and the bugs are causing some problems.

Just before 10:30 p.m. Sunday in Pierce Co., deputies say a three car crash happened on Hwy 63 near 825th street in the Town of Trenton near Hager City. 24-year-old Theresa Hunt of Ellsworth lost control on the slippery road covered in mayflies. Her car hit another car and a van. She was hurt, but refused to get transported to the hospital. One of the other drivers was taken to the hospital with unknown injuries.

The Wisconsin DNR said mayflies are full of protein and fat reserves right now. So when mayflies die, a mass of it will land on the ground, creating a greasy slickness so cars can easily lose traction.

“What happens is the spinners hit the ground. They’re sometimes accumulating in areas that are lit up at night; so street signs, any of the power poles that have power lights on them, those are objects that these animals will be attracted to,” said Harvey Halvorsen, Wildlife Supervisor with the DNR. “Especially the bridges, if bridges have lighting, the Hexagenia adults will be attracted to the bridges.”

The bugs only live for 48 hours and don’t bite humans, said Halvorsen. But they can be a pain to cleanup once they die.

Glen Siewer is the owner of Mr. Sippi, located on the Wisconsin Channel of the Mississippi River on Hwy 63 in the Town of Trenton.

“Where you're standing, there was two feet of water about three weeks ago and I think the flood has delayed their hatch this year because they're just starting to hatch and normally they start before the 4th of July,” said Siewer.

He had already collected four wheelbarrows full of mayflies since the morning.

“A lot of people don't like walking through them. The bridge up here gets extremely slippery. We have a couple of accidents just about every year due to the mayflies,” said Siewer.

The hatch was so intense, the National Weather Service picked it up on its radar. You can see a swarm of blue and green flying out from the Mississippi River.

“They become a nuisance in some regards; when they get this thick, when they hatch in mass right at sunset and they're found at any location that has good silty, water bottom and substrate,” said Halvorsen.

He said areas along the Mississippi and backwaters of the Chippewa and Eau Claire Rivers are perfect conditions for mayflies.

“They’re highly sought after by birds,” he said. “They like to use that for food resources.”

Fish are also attracted to the carcasses of the dead mayflies, making for good trout fishing along the rivers. Halvorsen said the pesky critters hatch in the millions, but because they die quickly, they create a mess on the roads.

“Sometimes, they have to plow the bridges and they'll dump sand because they end up real greasy when they get squished,” said Siewer.

The DNR said while it's hard to predict when there will be a mayfly hatch, we do know the hatch happens right at sunset. So if you're driving along the Mississippi River sunset or see a cloud of insects, try to avoid it. Don't use your windshield wipers because it'll create a bigger mess. Slow down when you’re driving and leave plenty of space between you and other cars because it's going to feel a lot like black ice. If you’re hiking or walking, stay away from the roadways because drivers’ visions could be impaired.

“Maybe some of the cities, if they want to reduce the attractiveness of the mayfly on the bridges, shut off the lights,” said Halvorsen. “If they can momentarily dampen the lighting on the bridges for the next couple of days during peak hatch, that would reduce attraction for the Hexagenia."

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